Nafion(R) 117-doped polyaniline films were prepared by two chemical methods. The preparation procedures were very similar, differing only in the timing of the doping step, i.e. before or after film preparation. The method involving direct doping of neutral polyaniline in N-methylpyrrolidone by the acid form of Nafion(R) is better. It enables the preparation of homogeneous films with electronic conductivities up to 0.3 S cm(-1) and a doping level of sulfonate groups of up to 30%. Electrochemical characterization reveals an improvement in the polyaniline doping-undoping process kinetics compared with that of pure polyaniline films. The increased metal-insulator transition kinetics is explained by a high lithium diffusion coefficient, of the order of 10(-7) cm(2) s(-1), and a molecular entanglement of both polymeric networks deduced from chronoamperometric experiments. The high cycle life and charge retention of this promising electrode material are demonstrated.